We intend to grow larger crystals of the modulator protein of adenyl cyclase (and of cyclic nucleotide phosphodiesterase) and to determine its structure at atomic resolution. This structure will be refined and interpreted in terms of its known amino acid sequence, physical properties and biochemical functions. We will try to obtain usable crystals of (1) whole troponin, (2) ionophoretic fragment of sarcoplasmic reticulum ATPase (Ca2 ion), (3) gamma-carboxy glutamic acid containing calcium binding protein of bone, (4) calcium binding protein of Limulus muscle, and (5) calcium binding protein of crayfish sarcoplasmic reticulum. I will continue my theoretical considerations of the evolution of the role of calcium as a second messenger and writing of related review articles.